The present invention relates to generally to laser treatments and, more particularly to an apparatus and method of laser treatment of subsurface cutaneous tissue for the purpose of effecting a tightening of the skin and reducing wrinkles without significantly altering the epidermis.
Pulsed CO.sub.2 lasers, erbium lasers, holmium lasers, and other infrared lasers are being used clinically to remove the epidermis and superficial reticular dermis for the purpose of laser resurfacing. Besides removing the superficial layers, there is often a significant contraction of the skin associated with these laser resurfacing technologies. This skin tightening is due to sufficient, but not excessive dermal collagen heating by the laser, and it is as important to patient satisfaction as the more youthful epidermis (skin surface) appearance achieved by laser resurfacing.
Unfortunately, in order to achieve this skin tightening, it has been necessary to remove the epidermis with the laser. This results in a raw skin surface that is unsightly, and that requires extensive wound care for weeks. Attempts to reduce these unwanted side effects by using lasers for resurfacing that do not produce undesired collateral thermal effect result in inadequate tightening of the skin. For example, a pulsed CO.sub.2 laser of 100 microseconds or so duration (e.g., Tru-Pulse, Tissue Technologies, Inc., Albuquerque, N. Mex.) cause less postoperative erythema, swelling, and discomfort than pulsed CO.sub.2 laser of one millisecond pulse duration (e.g., Nova-Pulse, Luxar, Inc., Redmond, Wash.), but they do not tighten the skin as much as the longer-pulsed CO.sub.2 lasers.
Wrinkle removal by pulsed infrared lasers during resurfacing is a result of removal of the epidermis and reticular dermis at the same time. Skin tightening requires deeper thermal effects than wrinkle removal. Thus attempts to reduce postoperative erythema, pain and swelling by doing a more superficial resurfacing do not result in adequate skin tightening.
Prior art has used computer-based video technology to quantify the amount of tissue contraction in vitro associated with different ablative lasers such as CO.sub.2 and erbium:YAG in order to compare their thermal effects. The in vivo use of such technology has been unnecessary and impractical because the ablative effects of the resurfacing laser would remove superficial ink marks necessary for analysis, and the end point of the treatment with ablative lasers is judged by the color appearance of the superficial dermis.
Prior art method such as those disclosed in U.S. Pat. Nos. 4,976,709 and No. 5,484,432, attempt to selectively treat subsurface collagen without damaging the surface have been primarily related to corneal treatment (laser thermal keratoplasty) for corrections of refractive errors using infrared wavelength greater than 1.8 micron. Moreover, treatment parameters identified were selected so as to avoid a cicatrix which might impair the transparency of the cornea. For example, preferred embodiments included small (&lt;2 mm in diameter) spot size, short pulse duration (0.1 sec), a fluence up to 100J/CM.sup.2 and non-contact delivery means.
Contact handpieces and non-contact delivery means for laser treatment of the eye have included designs which allow for surface-sparing of the ocular tissues, but delivery of a photocoagulation to internal tissues such as the ciliary body in glaucoma management. In U.S. Pat. No. 5,514,125, for example, a contact handpiece for delivery of laser energy to the ciliary processes in glaucoma is described. It features a fiberoptic distal member separated from a focusing lens at the contact tip for the purpose of reducing scatter of the laser energy.
Controlled subsurface laser energy also can be used to remove hair, tattoos and varicose veins. A contact subsurface laser energy delivery system that can target the follicle and not damage the sebaceous glands and sweat glands and the skin between the hairs would be advantageous. Further a system for removing tattoos and treating varicose veins by the controlled subsurface application of laser energy to a predetermined depth is desirable. Since tattoo pigment and varicose veins can be found in subepidermal locations or deeper into the dermis, an apparatus that can variably focus the laser energy to a predetermined depth is desirable.
It is desirable, therefore, to use a novel device and method to increase skin tone to reduce wrinkles (and striae) without causing damage to the skin surface. Further, it would be desirable to include an especially small contact mechanism for the thin skin of the eyelids. It also would be advantageous to utilize an in vivo mechanism to quantify the amount of skin contraction in order to assure the operator that the treatment is suprathreshold.